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![]() Changing API xdp_return_frame() to take struct xdp_frame as argument, seems like a natural choice. But there are some subtle performance details here that needs extra care, which is a deliberate choice. When de-referencing xdp_frame on a remote CPU during DMA-TX completion, result in the cache-line is change to "Shared" state. Later when the page is reused for RX, then this xdp_frame cache-line is written, which change the state to "Modified". This situation already happens (naturally) for, virtio_net, tun and cpumap as the xdp_frame pointer is the queued object. In tun and cpumap, the ptr_ring is used for efficiently transferring cache-lines (with pointers) between CPUs. Thus, the only option is to de-referencing xdp_frame. It is only the ixgbe driver that had an optimization, in which it can avoid doing the de-reference of xdp_frame. The driver already have TX-ring queue, which (in case of remote DMA-TX completion) have to be transferred between CPUs anyhow. In this data area, we stored a struct xdp_mem_info and a data pointer, which allowed us to avoid de-referencing xdp_frame. To compensate for this, a prefetchw is used for telling the cache coherency protocol about our access pattern. My benchmarks show that this prefetchw is enough to compensate the ixgbe driver. V7: Adjust for commit |
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appletalk | ||
arcnet | ||
bonding | ||
caif | ||
can | ||
dsa | ||
ethernet | ||
fddi | ||
fjes | ||
hamradio | ||
hippi | ||
hyperv | ||
ieee802154 | ||
ipvlan | ||
netdevsim | ||
phy | ||
plip | ||
ppp | ||
slip | ||
team | ||
usb | ||
vmxnet3 | ||
wan | ||
wimax | ||
wireless | ||
xen-netback | ||
dummy.c | ||
eql.c | ||
geneve.c | ||
gtp.c | ||
ifb.c | ||
Kconfig | ||
LICENSE.SRC | ||
loopback.c | ||
macsec.c | ||
macvlan.c | ||
macvtap.c | ||
Makefile | ||
mdio.c | ||
mii.c | ||
netconsole.c | ||
nlmon.c | ||
ntb_netdev.c | ||
rionet.c | ||
sb1000.c | ||
Space.c | ||
sungem_phy.c | ||
tap.c | ||
thunderbolt.c | ||
tun.c | ||
veth.c | ||
virtio_net.c | ||
vrf.c | ||
vsockmon.c | ||
vxlan.c | ||
xen-netfront.c |